The invention relates to a solenoid valve assembly of on/off type, which may find its application as a control valve for controlling the suction of an automobile, for example, in which a valve element which opens or closes a fluid path is repeatedly operated in an on/off manner so that a flow rate can be controlled by adjusting the duty cycle or the ratio of the on period to the off period.
In a solenoid valve assembly of the type described, a movable part or valve element is generally supported by a diaphragm in a displaceable manner, and a stationary core is disposed in opposing relationship with and close to a movable core which is secured to the valve element so that when the stationary core is excited magnetically by energizing an electrical coil, the movable core is held attracted by the stationary core. The movement of the movable core opens or closes the clearance defined between the valve element and the valve seat, and hence the fluid path of the valve.
In the solenoid valve assembly constructed in the manner mentioned above, a collision occurs between the movable and the stationary core as the movable core is attracted by the stationary core. Such collision is inevitable in a conventional solenoid valve. Consequently, in applications which employ a duty control in which the on/off operation is frequently repeated within a reduced length of time, percussion sounds of an increased magnitude occur continually, and the abrasion of parts which collides against each other shortens the useful life of the valve assembly.